Globally, organization and system-level interventions are needed to provide integrated services to address the needs of People Living with HIV who use drugs (PLHWUD) and other comorbid conditions. Coordination and networking among multiple healthcare agencies needs to be strengthened both vertically and horizontally. The community health and service workforce can be mobilized to promote service integration, which is particularly critical in low- and middle-income countries. The proposed study will develop and pilot test multilevel integration strategies in Vietnam, including structural changes for better treatment coordination, strengthening treatment-provider networks for improved service collaboration, and involving community health workers (CHW) to support those in need throughout the treatment cascade. The study will be conducted in six provinces in Vietnam. In Phase 1, we will conduct formative studies with 20 PLHWUD, 24 clinic providers from HIV and drug use treatment facilities, and six Directors of Provincial AIDS Centers. Based on the findings, we will establish a provincial coordination team at each participating province. In Phase 2a, we will implement and pilot test an agency-level intervention by training 72 service providers working at various HIV and drug treatment centers to enhance coordination and networking among providers and to improve their interactions with patients. Agency-level aggregated data will be collected and compared at the baseline and at 12 months after the intervention. In Phase 2b, we will implement and pilot test our intervention strategies that focus on CHW working at commune health centers (CHC) to enhance their networking and collaboration with providers at the treatment facilities. The intervention will also focus on improving CHW communication skills to support PLHWUD treatment initiation, retention, and adherence. To assess intervention outcomes, we will recruit 80 CHW and 240 PLHWUD from 40 CHC. Intervention outcomes on PLHWUD and CHW will be compared at baseline and every three months for one year.